Concentration effects on the Raman scattering of AlGaN/GaN superlattices

The calculation of the Raman spectra of AlxGa1−xN/GaN superlattices for the whole aluminum concentration range was performed in this work. The highest frequency modes are greatly influenced by the Al molar fraction. An interface with thickness varying in steps of one monolayer up to three was included. Severe changes in the middle frequency range of the Raman spectra are induced by the presence of interfaces. The changes in the atomic displacements and the phonon dispersion relations are discussed.